Porous titanium roots, which have supported masticatory function for periods of 1 to 2 years in rhesus monkey mandibular premolar sites will be adapted to serve as abutments for fixed bridgework in molar sites. Three unit bridges supported by a natural first molar with the implant serving as the distal abutment and three unit bridges with two implants as support will be evaluated. The basic objective of the research is to determine whether implants which have functioned successfully as free standing single tooth replacements in masticatory function can serve as well under occlusal function and to determine what implant design and technique modifications are necessary for this application. Detailed clinical evaluations will be conducted on the implants for periods ranging from 3 to 4 years. The inclusion of four monkeys which have successful premolar implants will result in data being obtained on these implants for up to 7 years. The length of time of implant function will allow subtle changes in gingival tissues and supporting structures which contribute to the success or failure of the implanted-supported prostheses to be evaluated. Selected monkeys will be sacrificed and the implants subjected to detailed histological evaluations. The results of this research will allow judgments to be made on whether an inert porous medium which undergoes boney ingrowth can be the solution to the problem of long term implant maintenance in humans.